Use of numerically controlled systems have greatly improved the speed and repeatability of such production techniques as welding, drilling and cutting. With the advent of laser technology it has been discovered that a laser can perform some production methods more accurately than standard mechanical tools. When combined with a numerically controlled machine, the laser provides a manufacturing system that can be both accurate and fast. Typically, numerically controlled gantry systems are capable of transversing a tool over a workpiece at 2,200-2,400 inches per minute (IPM). To properly utilize the potential of these gantry systems, the laser should be able to perform the working function, whether it is cutting, welding or drilling, at approximately the same speed as the gantry. Generally speaking, workrates for lasers is a function of laser power. To obtain a workrate in the order of 2,000 IPM, high powered lasers in the range of 400-2,000 watts are required.
Prior high powered laser gantry systems include the one disclosed in Swensrud, U.S. Pat. No. 4,661,680 which places a laser at a fixed position on the floor, and uses a laser delivery system to deliver a laser beam to the workpiece. When the workpiece is large, such as a sheet of airplane skin, a gantry in the range of 40 feet is required. Because the laser is stationary, the laser beam would have to travel at least 20 feet to perform work at the end of the gantry. Travelling long distances can result in excessive beam divergence, that can reduce the power of the laser when it reaches the workpiece.
Using a floor mounted laser can also result in unpredictable laser beam location as the beam travels through the laser delivery system. Typically, to deliver a laser beam to a workpiece, a series of mirrors is required to direct the laser to the location of the piece. To insure that the laser beam will be directed to the desired location, the reflection angle of the beam off the mirrors must be constant. If the laser is placed on the floor and the mirrors are attached to the gantry, any thermal expansion, vibration or shift of the gantry will move the mirrors relative to the laser, causing a change in the reflection angle, making laser beam location unpredictable.
Therefore, it is desirable to have a numerically controlled gantry with a high powered laser, that is in constant close proximity to a workpiece, and has a mirror delivery system that provides beam location.